Microdeletion 15q26.2qter and Microduplication 18q23 in a Patient with Prader-Willi-Like Syndrome: Clinical Findings.

The small interstitial deletion in the long arm of chromosome 15 causing Prader-Willi/Angelman syndrome is well known, whereas cases that report terminal deletions in 15q in association with the Prader-Willi-like phenotype are very rare. By using GTG-banding analysis, metaphase FISH, MLPA analysis, and genome-wide array CGH, we detected an unbalanced translocation involving a microdeletion of the distal part of 15q and a microduplication of the distal part of 18q. The unbalanced translocation was found in a boy that was referred with clinical suspicion of Prader-Willi syndrome. In the 15q-deleted region, 23 genes have been identified, and 13 of them are included in the OMIM database. Among these, the deleted IGFR1, MEF2A, CHSY1, and TM2D3 genes could contribute to the patient's phenotype. Seven genes are included in the duplicated chromosome segment 18q, but only one (CTDP1) is present in the OMIM database. We suggest that the deleted chromosome segment 15q26.2qter may be responsible for the phenotype of our case and may also be a candidate locus of Prader-Willi-like syndrome.

Chromosome mapping of Miller-Diecker, Smith-Magenis and RARA loci in non-human primates: implications in the evolution of human chromosome 17.

Molecular cytogenetics allows to verify chromosomal homologies previously hypothesised on the base of banding pattern comparison in different species. So far only the chromosome painting technique has been extensively used in studies of chromosomal evolution. This technique allows to detect only interchromosomal rearrangements. Human and Great Apes chromosomes basically differ by intrachromosomal rearrangements, in particular inversions; with chromosome painting it has just been possible to confirm the origin by fusion of human chromosome 2 and a reciprocal translocation in Gorilla, involving the homologous of chromosome 5 and 17. In order to verify intrachromosomal rearrangements in human chromosomal evolution, chromosome mapping of human loci in non-human primates is a useful approach. We mapped Miller-Diecker, Smith-Magenis and RARA loci localised on human chromosome 17, in Gorilla gorilla, Pongo pygmaeus, Macaca fascicularis and Cercopithecus aethiops. On the base of the obtained results it was possible to verify chromosomal rearrangements previously identified by banding, to achieve new informations about the controversial evolution of human chromosome 17, and to detect the occurrence of a paracentric inversion in the homologous in Cercopithecus aethiops.